[rrd-developers] Re: Stippled lines in libart?

Peter Speck speck at ruc.dk
Tue Apr 2 08:44:50 MEST 2002

On tirsdag, april 2, 2002, at 07:20 , Tobias Oetiker wrote:

>> There's one thing I'm really missing, which is the stippled grid line
>> from the GD version. It doesn't seem to be easy to do with libart. Is
>> this on someone's hit list already? I'd hate to reinvent the wheel...
> Hi Bert,
> nope, but I guess by tuning the color and transparency defaults for
> the current lines this should be feasible ... I also expect the
> promised eps driver to use dashed lines to approximate transparency

A few comments from eps/svg/pdf land: dashed lines are implemented as an 
attribute on the line just like color is. The dash is a full on/off 
functionality, so it basically chops the line into sublines.
The simplest implementation will have an attribute which is subline 
length for each dash. The next simplest version will have a separate 
length for the on-part and for the off-part. Having length = 0 could 
signal non-dashed line.
Transparency came rather late to pdf (version 1.4, Acrobat 5.0), so 
using it could probably be a problem for most non-Adobe pdf readers. 
EPS/Postscript does not have support for transparency, and it have to be 
faked somehow, if desireable. svg has transparency for it from version 

  - Peter Speck

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